1. Field of the Invention
The present invention relates to a movement detection device suitable for use with (i) a camera having a vibration-proof device for compensating for the movement of an image being picked-up by the camera due to trembling of the hand or other vibrations, (ii) an automatic tracking apparatus for tracking a moving object, or (iii) an automatic focus detection apparatus for detecting a focusing state from an image pick-up signal.
2. Related Background Art
Recently, image instruments such as a video camera or electronic camera have been remarkably developed in which, to enable a more reliable and appropriate photographing operation, a movement correction device has been adopted which allows the photographing of higher quality images without fluctuation by correcting the movement of the image due to trembling of the hand or other vibrations.
The movement correction method for the movement correction device involves (i) a mechanical correction method of using inertia to maintain the axes of the lens and image sensor fixed against the rotation of camera body, (ii) an optical correction method of using an optical member such as a variable apex angle prism, and (iii) an image processing correction method for making the correction by moving the image with image processing.
According to the mechanical correction method, a special structure for supporting the lens and a pick-up system is required. According to the optical correction method, a special optical member such as a variable apex prism is required, while in the image processing correction method, no special mechanical structure or optical members are necessary. In the image processing correction method, the movement is corrected only with signal processing using electrical circuitry, and this method is expected to be widely used in the future.
However, the movement correction device with the above-mentioned conventional image processing method has the following disadvantage, compared with the mechanical or optical device. That is, in performing the movement correction with the image processing method, an image has some movement at the pick-up stage (with an image sensor or pick-up tube), whereby in the post-pick-up processing, the movement of the image within an image screen is removed by shifting the image in accordance with the amount of image movement.
Thus, as the image obtained in the pick-up stage yields some unfocused portions, final resolution of the image is low even if the movement of the image is corrected in the post-pick-up processing, so that a poor quality of image is output.
Recently, in video instruments such as a video camera or an electronic camera, an automatic focusing adjustment apparatus for adjusting the focus by detecting the focusing state from a pick-up signal has been adopted, but as above described, the movement of the image may reduce a high frequency component varied with the focusing state from the pick-up signal, thereby decreasing the sharpness, and degrading the performance of automatic focusing adjustment apparatus, whereby there is a risk of a malfunction. Thus, it is quite important to detect and correct the movement of the image in the signal processing using the pick-up signal.